Gaseous fuel-powered engines are common in locomotive applications. For example, the engine of a locomotive can be powered by natural gas (or another gaseous fuel) alone or by a mixture of natural gas and diesel fuel. Natural gas may be more abundant and, therefore, less expensive than diesel fuel. In addition, natural gas may burn cleaner in some applications.
Natural gas has traditionally been introduced radially into an engine's cylinders, to mix with air therein as an associated piston moves toward a top-dead-center (TDC) position. In some applications, a natural gas nozzle is situated to inject gaseous fuel through an existing air inlet port located within an annular surface of the engine's cylinder liner. Although somewhat effective, injecting gaseous fuel at this location can also be inefficient. In particular, some of the injected gaseous fuel may pass back out through the same air inlet port (or back out through another air inlet port) into an associated air box. In addition, injecting at this location results in advanced injection timing that can allow some of the injected fuel to exit the cylinder via still open exhaust valves. In either situation, some of the gaseous fuel is being wasted.
An exemplary dual-fuel natural gas/diesel engine is disclosed in U.S. Pat. No. 5,035,206 of Welch et al. that issued on Jul. 30, 1991 (“the '206 patent”). The engine includes a cylinder, a piston in the cylinder, and inlet ports around the cylinder that are uncovered by downward movement of the piston. A blower forces air through the inlet ports, and an injector is provided for injecting natural gas into the cylinder once during each cycle. The injector has a delivery conduit that opens into the cylinder at a location above the air inlet ports. When the piston is descending, the piston completely uncovers the delivery conduit before beginning to uncover the air inlet ports. In this configuration, the natural gas is timed for injection as late as possible, preferably after the piston reaches bottom-dead-center (BDC), and continues until after air entry has been stopped by upward movement of the piston. This provision ensures that a large portion of air will have filled the cylinder before the entry of natural gas, so as to minimize the escape and loss of natural gas.
Although the engine of the '206 patent may help to reduce the loss of natural gas, it may only be applicable to air-cooled engines and/or newly manufactured engines. In particular, the delivery conduit of the '206 patent may not be compatible with a liquid-cooled engine having a water jacket formed around the cylinder. Further, the '206 patent provides no way to retrofit an existing engine with the delivery conduit. In addition, injecting gaseous fuel during air introduction may still lead to reverse flow of the gaseous fuel out of the inlet ports.
The engine system of the present disclosure solves one or more of the problems set forth above and/or other problems in the art.